Membranes hormone effect

Selected entries from Methods in Enzymology [vol, page(s)] Chelation, 238, 74, 76, 297 buffers [for analysis of exocytosis, 221, 132 preparation, 219, 186 modulation of cytosolic buffering capacity with quin2, 221, 159] fluorescence assay, 240, 724-725, 740-742 fluorescence imaging, 225, 531 238, 303-304, 322-325, 334-335 free intracellular levels after bacterial invasion, 236, 482-489 free calcium in solutions for membrane fusion analysis, calculation and control, 221, 149 homeostasis mechanisms, 238, 80 hormonal elevation, 238, 79 inositol phosphate effect on release, 238, 207 determination of cytosolic levels [computer methods, 238, 73-75 with fura-2, 238, 73, 146 with indo-1, 238, 298, 316-317 with quin-2, 238, 297] hormone effects, 238, 79 ionomycin effects, 238, 79 membrane depolarization effects,... 

Clearly, major differences seem suggested in the mechanisms of hormone-membrane receptor interactions leading to various post-binding events [11], For FSH, as an example, there have been reports of hormone effects on membrane potentials of cultured Sertoli cells [12] and on conductance of artificial lipid membranes [13], as well as on amino acid transport systems [14]. Indeed, there has been one report of receptor-mediated gonadotropin action without receptor occupancy... 

Wehling M, Losel R. Non-genomic steroid hormone effects membrane or intracellular receptors J. Steroid Biochem. Mol. Biol. 2006 102 180-183. 

Once produced within the cell, c-AMP seems to have the activation of protein kinase as its main function. This activation in turn phosphorylates particular postsynaptic proteins in the cell membrane. This results in the alteration of pores facilitating cation passage. As a second messenger it facilitates the action of more than a dozen hormones besides NE/EP, including ACTH, insulin, lipotropin, calcitonin, and vasopressin. To the extent that they are tested experimentally hormonal effects could be mimicked by exogenous addition of c-AMP. 

Thyroid hormone effects on metabolism arc diverse. The rates of protein and carbohydrate synthesis and catabolism are inlluenced. An example of the effect of thyroid hormones on lipid metabolism is the observation of a high serum cholesterol in some hypothyroid patients. This is a consequence of a reduction in cholesterol metabolism due to down regulation of low-density lipoprotein (LDL) receptors on liver cell membranes, with a subsequent failure of sterol excretion via the gut. 

Enhanced expression of neoplasm Inhibited differentiation Stimulated cellular proliferation Cytotoxic effects Hormonal effects Cell membrane effects Induction of proteases... 

Hormonal effects occurring via membrane receptors tend to be of short duration because they represent responses to rapid and urgent physiological demands and involve activation or inhibition of preexisting enzymes. 

For cell membranes to be effective permeability barriers, they must be flexible and allow relatively free motion of proteins that are embedded in or linked to them. Integral membrane proteins often diffuse laterally, and many receptor-mediated solute-uptake pathways involve endocytosis that entails phospholipid rearrangement in the membrane. Hormone secretion and other protein trafficking processes involve exo-cytosis and it is usual for membrane vesicles to fuse with each other in a process that also involves the lateral diffusion of membrane constituents. The activity of some receptors is strongly linked to the extent of fluidity of the membrane around them. 

As with other hormone effects, steroid hormones act by attaching to a protein receptor molecule. The fact that such small chemical differences among these basically very similar steroid molecules can result in such profoimdly different effects is just another indication of the extraordinary power of selective molecular recognition by protein molecules. Unlike the receptors for many other hormones, receptors for steroid hormones are not embedded in the cell membrane. They do not need to be because these hormone molecules are both small and hydrophobic... 

Although cortisone interferes with protein synthesis in peripheral tissue, the hormone stimulates protein synthesis in liver. The increased rate of protein synthesis results from an effect of the hormone on the penetration of the amino acid through the cell membrane. The effects of the steroid hormones on the amino acid penetration were demonstrated with the aid of a-aminoisobutyric acid, a nonmetabolizable amino acid the intracellular penetration of which is regulated by mechanisms similar to those controlling glycine penetration. The penetration of a-aminoisobu-tyric acid is competitively inhibited by valine. Two hours after the injection of cortisol, the aminoisobu-tyric acid content of the liver is increased 70%. The increase in amino acid uptake may explain the increase of protein synthesis in liver observed early after cortisone injection. In that connection, it is of interest that an accelerated turnover of serum albumin has been reported early after the injection of cortisone. Since the concentrations in the levels of the blood protein are not changed, it seems that increased synthesis only compensates for increased catabolism. 

Contents The Wall of Growing Cells. — Hormones. — Membranes. — Hormone Analysis. — Auxins and Root Growth Inhibitors. — Gibberellins and Cytokinins. — Ethylene and Other Regulators. — Gravity and Light Effects. 

Growth increases may be initiated by various effects of rare earth application, particularly those of membrane stabilization, improved hormone effectiveness, growth responses in coleoptile segments, improved nitrogen fixation and efficiency and a reduction in water loss by the plant. 

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